Several ways to archive...
• Store on removable hard drives, but as mentioned drives can fail when not properly stored.
• Record footage back to tape. Yes I did say record digital footage back to tape. This might seem stupid, but tape is still one of the best archival methods.
• Burn data on DVD or BluRay media. Make sure that you use good, not cheap media, as cheap DVD's don't have the best shelf life. I have unfortunately found out first hand.

It's probably best to use 2 of the 3 methods. As it's never recommended to place all of your eggs in one basket, as redundancy is always best.
I would most likely archive footage to hard drives, as well as burn the media on Dual layer DVD or BluRay disk. It's highly unprobable, that both archival methods would fail, but anything is possible. So if let's say your hard drive fails, then you ahve the disk for backup and visa versa.

For myself and my editing anyway, I always ahve the media that I am currently editing on my system drive, and also ahve extrenal ESATA drives for backup purposes. These drives have the exact same information on them that the system drives do (media, NLE files, artwork etc.). So If I was editing with AVCHD media (which I still currently use tape), then I would archive the native fooatge on my system drive, ready for transocding when the edit needs to happen, as well as on external drive for backup purposes. I woudl also burn them to disk for additional backup. When the vidoe is finished, I would send the final edit to tape for archiving, and store on drives for additional archival. Hard drives aren't bad for storage, but you must make sure that you seal them properly and store them in a standing position, and plug them in every couple of months and let the drive spin up, and then remove it for storage. If the drive doesn't spin up for prolonged periods of time, then the drives are prone to lose the data on the disk.